Assertion : Besides chlorophyll a, blue - green and red algae show the presence of phycobiliproteins .
Reason : Chlorophyll and phycobiliproteins are integrated into thylakoids.

Options

A. If both A and R are true and R is the correct explanation of A
B. If both A and R are true but R is not the correct explanation of A
C. If A is true but R is false
D. If both A and R are false

Answer

To solve the question, we need to analyze both the assertion and the reason provided.

### Step-by-Step Solution:

1. **Understanding the Assertion**:
- The assertion states that "Besides chlorophyll a, blue-green and red algae show the presence of phycobiliproteins."
- Blue-green algae (cyanobacteria) and red algae (rhodophytes) are known to contain chlorophyll a as well as additional pigments.
- Phycobiliproteins, which include phycoerythrin (red pigment) and phycocyanin (blue pigment), are indeed present in these algae.
- Therefore, the assertion is **true**.

2. **Understanding the Reason**:
- The reason states that "Chlorophyll and phycobiliproteins are integrated into thylakoids."
- Chlorophyll is located in the thylakoid membranes of chloroplasts, where it plays a crucial role in photosynthesis.
- However, phycobiliproteins are not located in the thylakoids; they are found in the stroma of the chloroplasts in red algae and cyanobacteria.
- Thus, the reason is **false**.

3. **Conclusion**:
- Since the assertion is true and the reason is false, the correct answer is that the assertion is true but the reason is false.

### Final Answer:
The correct option is **third**: Assertion is true but reason is false.

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